This invention pertains to portable devices for raising and sustaining for long periods in a raised position parts of machines, and more particularly, to an improved and strengthened scissor jack for lifting automobiles or tractors from a position beneath such parts.
As is well known, automotive parts such as engines, transmissions, differentials, etc., are generally too heavy to be lifted without some mechanical assistance. In addition, it is frequently impossible to lift these parts from above by a hoist or overhead lifting device because such parts are inaccessible, or because a breakdown has occurred in some remote place. Therefore, it has become fairly common to use a lifting jack which, when fully collapsed, can be placed easily under a car and raised from that position to lift the car or any part thereof off the ground.
Generally, portable jacks which may be transported in the trunk of an automobile and are widely available to the consuming public, are characteristically made for emergency use rather than everyday use. These jacks employ compromising design structures which will fatigue if used repeatedly. Some of these portable jacks represent substantial hazards to the user because of improper designs which can cause the jack to shift off center in actual use.
Accordingly, it is an object of this invention to provide an improved jack design that is both strong, stable, and durable which can be produced in quantities at relatively low costs.
It is also an object of this invention to furnish a portable scissor jack which compensates for shifts in a lifted load thereby avoiding tilting, or off-center, loads from prematurely collapsing the jack.